In modern semiconductor device applications, numerous components are packed onto a single small area, for instance, on a semiconductor substrate, to create an integrated circuit. For the circuit to function, many of these individual components may need to be electrically isolated from one another. Accordingly, electrical isolation is an important and integral part of integrated circuit design for preventing the unwanted electrical coupling between adjacent components and devices.
As the size of integrated circuits is reduced, the components and devices that make up the circuits must be positioned closer together in order to comply with the limited space available. As the industry strives towards a greater density of active components per unit area, effective isolation between circuit components becomes all the more important.
Isolating circuit components in modern integrated circuit technology may take the form of gap structures positioned between such circuit components. For instance, air gaps may contribute to isolation of interconnect lines that supply electrical power to various devices forming part of, or connected to, the integrated circuit. To further contribute to such isolation, a dielectric material may be deposited on the sidewalls and bottom of the gaps. In some instances, an oxide precursor material may be deposited over the top of interconnect lines and into the intervening gaps between the interconnect lines, which may be converted into an oxide having dielectric properties, such as silicon dioxide, by subsequent exposure, for instance, to oxygen.
As the density of components on the integrated circuit increases, the widths of certain components sometimes decreases, leading to increasing the height of such components to maintain a cross-sectional area adequate for desired current flow, such as in interconnect lines. To maintain isolation of such components from each other, for instance, intervening air gap structures correspondingly may increase in depth while also decreasing in width until the process of forming a dielectric oxide from the oxide precursor material on the bottom and sidewalls of the air gaps develops problems.
Constrictions may develop due to a narrow opening at the top of a gap, which may be exacerbated by depth of the gap, as the oxide precursor material is deposited around the two upper edges of the gap. Such constrictions may reduce exposure of the oxide precursor material at the bottom and adjacent sidewalls of, for instance, an air gap to a subsequent condition intended to convert the oxide precursor material to an effective dielectric oxide. For instance, inadequate exposure of a silicon-containing compound to oxygen may contribute to a silicon-rich mixture at the bottom and adjacent sidewalls of an air gap that has a high dielectric constant relative to the intended dielectric constant of a more uniform silicon dioxide.
As such, premature closing at the top of an air gap may reduce formation of an intended substantially uniform dielectric oxide layer at the bottom and adjacent sidewalls of the air gap. Hence, an effective dielectric constant of the resultant oxide mixture at the bottom and adjacent sidewalls of the air gap may be increased so as to reduce isolation of the components of the integrated circuit, such as neighboring interconnect lines.